glsl: add has_shader_image_load_store()

Preliminary work for ARB_bindless_texture which can interact
with ARB_shader_image_load_store.

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>

src/compiler/glsl/builtin_variables.cpp

@@ -840,8 +840,7 @@ builtin_variable_generator::generate_constants()
                 state->Const.MaxTransformFeedbackInterleavedComponents);
    }
 
-   if (state->is_version(420, 310) ||
-       state->ARB_shader_image_load_store_enable) {
+   if (state->has_shader_image_load_store()) {
       add_const("gl_MaxImageUnits",
                 state->Const.MaxImageUnits);
       add_const("gl_MaxVertexImageUniforms",

src/compiler/glsl/glsl_parser.yy

@@ -1318,8 +1318,7 @@ layout_qualifier_id:
       }
 
       /* Layout qualifiers for ARB_shader_image_load_store. */
-      if (state->ARB_shader_image_load_store_enable ||
-          state->is_version(420, 310)) {
+      if (state->has_shader_image_load_store()) {
          if (!$$.flags.i) {
             static const struct {
                const char *name;

src/compiler/glsl/glsl_parser_extras.h

@@ -330,6 +330,11 @@ struct _mesa_glsl_parse_state {
              is_version(400, 320);
    }
 
+   bool has_shader_image_load_store() const
+   {
+      return ARB_shader_image_load_store_enable || is_version(420, 310);
+   }
+
    void process_version_directive(YYLTYPE *locp, int version,
                                   const char *ident);